Your Betta is going into his third year...correct?
Some of the what you are seeing could be age related issues if they started over the last 30 days or so along with water quality issues
Long term salt can affect the kidneys, it is a great short term treatment product IMO/E
Water changes I would increase to 50% weekly on a regular basis at least...but even better in a 5g to make twice weekly 50% with gravel vacuum with one water change a week.
When sick or seeing behavior changes, wounds...etc....making daily water changes to help keep the pathogen/bacteria/parasites diluted has always helped my fish.
Freshwater fish need fresh water to thrive not just survive.
He could be snagging his fins on the plastic plants, use a pair of pantyhose and run over the plants and if they snag the betta fins will snag too.
What are your water pram numbers: ammonia, nitrite, nitrate, pH and water temp
Most fish will adapt to the pH without issue the sudden changes can be stressful if not deadly especially when you don't use buffers.
IMO/E the less chemicals the better
The betta is the only fish in the 5g tank correct......

Your Betta is going into his third year...correct?
Some of the what you are seeing could be age related issues if they started over the last 30 days or so along with water quality issues
Long term salt can affect the kidneys, it is a great short term treatment product IMO/E
Water changes I would increase to 50% weekly on a regular basis at least...but even better in a 5g to make twice weekly 50% with gravel vacuum with one water change a week.
When sick or seeing behavior changes, wounds...etc....making daily water changes to help keep the pathogen/bacteria/parasites diluted has always helped my fish.
Freshwater fish need fresh water to thrive not just survive.
He could be snagging his fins on the plastic plants, use a pair of pantyhose and run over the plants and if they snag the betta fins will snag too.
What are your water pram numbers: ammonia, nitrite, nitrate, pH and water temp
Most fish will adapt to the pH without issue the sudden changes can be stressful if not deadly especially when you don't use buffers.
IMO/E the less chemicals the better
The betta is the only fish in the 5g tank correct......

I'm not saying you're wrong on the salt, I'm positive you know more about this than I do, but I've read on numerous sites that small amounts of aquarium salts help protect your fish against fungus and parasites. Here's one http://www.bettatalk.com/water.htm - now I don't know if that is true or not because I've only been doing it for about a month so my experience in the matter is limited.

I have already started ick treatment. I found a site that says to treat the tank for 7 days with quick cure and raise the temp to 84 for the first 2 days then slowly decrease to 80. Add Melafix to help heal any abrasions. I've removed the carbon filter as well. So I guess my question to you now is if I have started this treatment, do you think it's wise to stop treatment and just do the water changes or should I continue treatment and the water changes along with it?

And about the daily changes, How do you do that exactly? I've read that you use aged water. Can you just take a 1 1/2 gallons out and 1 1/2 gallons tap water with ph decreaser and tap water conditioner before you put the water back in?

I've done the panty hose test and the plants don't snag. The plants are all on the bottom of the tank anyway and he never goes down there. He stays at the top.

What is your pH? A stable PH is ALWAYS better than a fluctuating one. Bettas are strong fish, then can definitely live through weird pH, unless you have a pH of 9, or 1, or something. I'm assuming your 7.4pH is with the decreaser. It'll just increase again, it's not stable. If it keeps fluctuating like that, it is REALLY bad for your betta - or at least worse than just keeping it at 8 or something. I'd recommend stop using the pH decreaser, and do very small constant water changes to raise the pH

Water changes - Google up 'siphon' that's what I use, and I stick it into the gravel to get the dirt out that way. And you don't necessarily HAVE to use age water,I don't either. Just take the water out, and put treated water back in. IMO, only use dechlorinator. That is all you'll ever need with your betta, and clean water. And for the treatment, don't stop it yet, you might as well finish it. But after this, definitely do water changes more often. And when you're done with treatment, try to get the temp. down to around 78-80.

Aquarium salt is always going to be debateable. Some use it religiously, some only use it temporarily for those certain times, it's up to the fish owner. I've seen people get bashed for using salt constantly (which I think is really unnecessary to bash someone for that). Again, it's your choice. I'm not sure about the long-term effects, though. Good luck with him, and sadly, he is getting quite old. Nice to know he's been there for a while, and if you get told something by the LFS, go to us first :)

Ah- and about the circles in his eyes, his eyesight may go down. I believe they're cataracts for fish. Pretty common in old age. if you see him missing food in the future, you'll know why. :)

What is your pH? A stable PH is ALWAYS better than a fluctuating one. Bettas are strong fish, then can definitely live through weird pH, unless you have a pH of 9, or 1, or something. I'm assuming your 7.4pH is with the decreaser. It'll just increase again, it's not stable. If it keeps fluctuating like that, it is REALLY bad for your betta - or at least worse than just keeping it at 8 or something. I'd recommend stop using the pH decreaser, and do very small constant water changes to raise the pH

Water changes - Google up 'siphon' that's what I use, and I stick it into the gravel to get the dirt out that way. And you don't necessarily HAVE to use age water,I don't either. Just take the water out, and put treated water back in. IMO, only use dechlorinator. That is all you'll ever need with your betta, and clean water. And for the treatment, don't stop it yet, you might as well finish it. But after this, definitely do water changes more often. And when you're done with treatment, try to get the temp. down to around 78-80.

Aquarium salt is always going to be debateable. Some use it religiously, some only use it temporarily for those certain times, it's up to the fish owner. I've seen people get bashed for using salt constantly (which I think is really unnecessary to bash someone for that). Again, it's your choice. I'm not sure about the long-term effects, though. Good luck with him, and sadly, he is getting quite old. Nice to know he's been there for a while, and if you get told something by the LFS, go to us first :)

Ah- and about the circles in his eyes, his eyesight may go down. I believe they're cataracts for fish. Pretty common in old age. if you see him missing food in the future, you'll know why. :)

I just tested my tap water and the PH is between 7.8 and 8.0. I just don't know what to do about that. I'm starting to think he's lasted for the past 2 1/2 to 3 years with this water at this PH and I'm horribly throwing him off by trying to regulate it to the standard PH level for bettas. Yes, you are right about the salt. To some it's a wonder drug, to others death in a scoop. That goes the same for the Melafix too
Soooooo confused

I wouldn't worry about the pH. He's used to it now, so I would stop using the pH decreaser. Bettas have a pretty large range when it comes to the tolerance of it. My pH is a higher number as well and I have not had any problems.

Does he still have ick?! if not, I would lower the temperature to about 79F.
You should always do water changes when bettas are sick. Usually more often than when they're not.

If you're still in treatment, and whether he has visible ick or not, keep treatment until it's actually over. If you end it early, it can still come back. How many days are left? And I think the only and best way to actually get appropriate pH is by buying yourself an Indian Almond Leaf (IAL). But I don't use this personally, so I can't answer questions about it. I've seen ph worse than 8. The betta will definitely live through that, don't worry! Definitely, definitely stop using the pH decreaser.

The great salt debate has been going on for a long time and in the research I have done along with the problems I have seen with my own tanks and fish with long term use I have chosen not to use it long term, I do, however, use both aquarium and epsom salt short term for treatments.
Reasons I no longer use aquarium salt long term and from research and scienitific studies/theories: some species of fish and plants are sensitive to both long and short term use, long term use can cause internal damage and this is when you can see symptoms like bloat, dropsy, vision problems, behavior changes to name a few, long term use can also cause resistance in pathogens/parasite, a current problem that is now being address with salt resistant ich from over use, under use and using wrong dosages. Kind of like antibiotic use, over use can sometimes cause more harm than good just as in medication and humans use/overuse/wrong use...etc.....
But I do agree its use is a personal choice, I don't use it for reason stated, but I do not "bash" people that do use long term, I just try to inform/educate others to why you should not use it long term.....

Once you start a treatment you should complete it as per the instruction on the label, unless they have a negative response/reaction to the medication/treatment, I also need to mention that mixing different medication/treatment all at the same time can cause adverse reaction or negative outcomes and you should be careful when doing so.

I rarely if ever use OTC medication as I have found that these can cause more harm than good in some cases and I have found better methods that are less harsh on the fish and tank as a whole.

IMO/E-the best medication is fresh water, often this will cure or improvement will be seen after one water change alone.
Understanding the science and the water quality as it relates to fish can be helpful, understanding how ammonia can burn the fish and long term effect from scar tissue that developed from ammonia burns, and how nitrite can affect the hemoglobin and oxygen transfer in the blood and how high nitrates can affect the immune response in fish can help one be a better fish keeper IMO.
pH can also be an issues and the sudden changes can adversely affect fish and pH can change how ammonia affect fish and the cycle..Fish are pretty tough and will adapt.... it is those sudden changes that can get them in some cases
Knowing the why and what for..... can be fun too....IMO

Water changes: I don't age my water but some do, it all depends on your water in how you need to treat it IMO

To make daily water changes, remove half the water and replace with like temp dechlorinated water, and when making daily partial water changes only vacuum the substrate/gravel one time a week to keep the good bacteria alive, however, when you are using OTC medication I would follow those direction as far as water changes to maintain therapeutic antibiotic levels.
Most antibiotics can't tell the difference between good and bad bacteria and can kill your nitrogen cycle and you may need to re-cylce the tank.

Once antibiotic are completed try water changes and see if that perks him up.

But I do agree its use is a personal choice, I don't use it for reason stated, but I do not "bash" people that do use long term, I just try to inform/educate others to why you should not use it long term.....

Apologies if you thought I was referring to you - I was definitely not!

The occasional bashing from other people on the salt-debate is highly unecessary. It's a bit more than "they're FRESHWATER fish, they don't NEED SALT" kind-of thing. Adding salt doesn't make it salt water. Just wanted to throw that out there, it's been bothering me for a while :)

Apologies if you thought I was referring to you - I was definitely not!

The occasional bashing from other people on the salt-debate is highly unecessary. It's a bit more than "they're FRESHWATER fish, they don't NEED SALT" kind-of thing. Adding salt doesn't make it salt water. Just wanted to throw that out there, it's been bothering me for a while :)

Not at all......I am a believer that there are more than one right and wrong way for everything....lol...and what works for me won't for someone else...not all tank are created equal....to many things can vary and change the equation....lol.....
And I really dislike sites and have very little respect for people that bash other because of the way they practices fish keeping and I hope that I did not sound that way...as that was not my intent...just too many variables at play in fish keeping...IMHO.....
And so true some freshwater fish do need/require salt at different stages of their life.... but it is marine salt that those species usually require, kinda like mollies and other species considered freshwater and/or sold out of freshwater tanks.... sometimes these guys will benefit if not require long term marine salt...not aquarium salt IMO/E anyways......
And again..Sorry if I offended anyone......not my intent.....

Not at all......I am a believer that there are more than one right and wrong way for everything....lol...and what works for me won't for someone else...not all tank are created equal....to many things can vary and change the equation....lol.....
And I really dislike sites and have very little respect for people that bash other because of the way they practices fish keeping and I hope that I did not sound that way...as that was not my intent...just too many variables at play in fish keeping...IMHO.....
And so true some freshwater fish do need/require salt at different stages of their life.... but it is marine salt that those species usually require, kinda like mollies and other species considered freshwater and/or sold out of freshwater tanks.... sometimes these guys will benefit if not require long term marine salt...not aquarium salt IMO/E anyways......
And again..Sorry if I offended anyone......not my intent.....

Don't worry, you didn't offend anyone at all. And those sites I steer clear of, it's no fun when you're in the fish hobby with people yelling at you.